Esters of imidodiphosphoric acid



United States Patent 3,253,063 ESTERS 0F MIDGDIPHOSPHORIC ACID Morris L. Nielsen, Dayton, Ohio, assignor to'Monsanto Company, a corporation of Delaware No Drawing. Filed Dec. 1, 1961, Ser. No. 156,480 4 Ciaims. (Cl. 260971) The present invention relates to a process for the manufacture of esters of imidodiphosphoric acid such as tetraphenyl imidodiphosphate, as well as other esters such as tetraalkyl and tetraaryl imidodiphosphates.

It is an object of the invention to prepare various esters of imidodiphosphoric acid which are of utility as insecticides and biological toxicants, and as intermediates in the preparation of sequestering agents and alkaline builders for detergent compositions.

The reactants employed in the present invention are the group of unsubstituted, the nitro-substituted and the sulfonate-substituted alkyl and aryl orthophosphates. Examples of alkyl and aryl phosphates include ethyl, benzyl, phenyl, and naphthyl orthophosphates of the general formula R PO where R is an organic group having from 1 to 16 carbon atoms. This phosphate is reacted with an alkali amide such as sodium amide. It has been found that the desired compounds are obtained in high yield when this reaction is carried out at a temperature of from 60 C. to 250 C., or preferably from 80 C. to 200 C. In this temperature range the numerous possible by-products and co-products which are theoretically possible have been found to be minimized.

The organic phosphate compound and the alkali metal amide are employed in the general proportion of from 0.5 to 4.5 or preferably from 1.5 to 2.0 gram moles of amide per gram atom of phosphorus. A specific preferred example is 1.5 gram moles of amide per gram atom of phosphorus.

The nitrogen-containing esters of the present invention such as tetramethyl, tetraethyl, tetrabutyl, tetraphenyl, tetracresyl, and tetra(nitrophenyl)imidodiphosphates are not readily obtainable by direct synthesis. However, it has been found that the present nitrogen-containing esters may be obtained by removing the metal content of the above salts but with the retention of the nitrogen. The process of removing the metal is carried out by ion exchange such as with an acid-treated zeolite or a sulfonated polystyrene resin. A preferred method however is to contact the aforesaid metal derivative with an acid having a dissociation constant of at least 1 x such as hydrochloric, hydrobromic, hydroiodic, hydrofluoric, sulfuric, sulfurous, phosphoric, phosphorous acids and hydrogen sulfide.

The following examples illustrate specific embodiments of the present invention:

Example 1.-Preparati0n of tetraphenyl imidodiphosphate The sodium derivative is first prepared as follows:

Six and six-tenth grams of commercial sodium amide (0.15 mole) and 23.6 g. of triphenyl phosphate (0.072 mole) are heated in 250 ml. toluene (previously freed from Water by azeotroping) at reflux. As the reaction proceeds, ammonia is evolved and the mixture thickens somewhat due to the formation of finely divided solids. After two hours reaction, the mixture is cooled to about 50 C. and the solids (crude sodium phenoxide) separated by centrifugation. After several washings of the solids with benzene they are set aside and the benzene solution added to the toluene centrifugate. The toluene and benzene are boiled off, leaving a viscous liquid which is taken up in 200 ml. benzene. This contains the desired sodium derivative of tetraphenyl imidodiphosphate.

To remove sodium ions and to isolate the tetraphenyl 3,253,063 Patented May 24, 1966 imidodiphosphate, the benzene solution of the sodium derivative is shaken with several portions of Water containing sufficient hydrochloric acid to maintain an acid condition. The benzene layer is separated and evaporated to about 50 ml. On adding hexane gradually there is precipitated 12.3 g. tetraphenyl imidodiphosphate as shown by its n.m.r. (nuclear magnetic resonance) peak at +11.2 p.p.m relative to H PO An additional quantity of 1.0 g. is obtained by evaporating the benzene-hexane supernatant layer. Recrystallization of the crude products from benzene solution by adding hexane yields the tetraphenyl imidodiphosphate melting at 113 C. (lit. 1l02 C., Kirsanov and Zhmurova, Chemical Abstracts, 53, 3118i (1959)) and having an identical X-ray diffraction pattern to that of the authentic material. The three most intense diffraction lines are given as follows, where the spacings in Angstroms are followed in parenthesis by their relative intensities:

9.9 A. 4.54 A. (60); 9.2 A. (40) Example 2 Hydrogen sulfide is bubbled through a slurry of the silver derivative of 1.7 g. tetraphenyl imidodiphosphate in 75 ml. benzene at room temperature for 1 hour. Black silver sulfide is formed. The solids are removed from the filtrate under vacuum. White solids are recovered melting at 1l2113 C. (lit. l2 C. for tetraphenyl imidodiphosphate). This preparation was also conducted with hydrochloric acid and the silver chloride removed to yield the tetraphenyl imidodiphosphate.

What is claimed is:

1. Process for making an imidodiphosphate ester Where R is selected from the group consisting of the unsubstituted, the nitro-substituted, and the sulfonate-substituted saturated alkyl radicals having from 1 to 16 carbon atoms and aryl radicals having from 6 to 16 carbon atoms which consists of, contacting an N-metal derivative selected from the group consisting of the alkali and alkaline earth derivatives of an imidodiphosphate ester, with an acid having a dissociation constant of at least 1 x 10 2. Process for making an imidodiphosphate ester where R is selected from the group consisting of the unsubstituted, the nitro-substituted and the sulfonate-substituted saturated alkyl radicals having from 1 to 16 carbon atoms and aryl radicals having from 6 to 16 carbon atoms by removal of metal atoms which consists of reacting an N-metal derivative of a metal of Groups IVB, V-B, VIB, VII, IV, II-V, III-A, IV-A and V-A of the Periodic Table of an imidodiphosphate ester, with hydrogen sulfide, whereby the metal atoms are replaced by hydrogen atoms.

3. Process for making tetraphenyl imidodiphosphate by acidifying the N-sodium derivative of tetraphenyl imidodiphosphate with hydrochloric acid.

4. Process for making tetraphenyl imidodiphosphate by reacting the N-silver derivative of tetraphenyl imidodiphosphate with hydrogen sulfide until the silver content has been transformed to silver sulfide.

References Cited by the Examiner UNITED STATES PATENTS 2,361,624 10/1944 Hamilton et al.

2,886,595 5/1959 Teinemann et a1. 260559 CHARLES B. PARKER, Primary Examiner. MORRIS LIEBMAN, Examiner. 

1. PROCESS FOR MAKING AN IMIDODIPHOSPHATE ESTER 